2012 500 EXC backfiring on deceleration? - KTM Forums: KTM Motorcycle Forum
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post #1 of 50 (permalink) Old 10-11-2011, 10:38 AM Thread Starter
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Question 2012 500 EXC backfiring on deceleration?

Hi. I just sold my 2008 530 EXC which was in brand new condition, and purchased a 2012 500 EXC to replace it with and so far I feel I could have made a mistake, and I don't want that to be the case. I feel the EFI isn't properly tuned or something, possibly too lean on idle because it backfires upon deceleration EXTREMELY BAD, and non-stop. I understand that a main cause for backfiring upon deceleration is an exhaust leak but I can't see, hear, or feel any exhaust leak which makes me think that the EFI is just simply tuned too lean on idle or something like that.

Can anyone here please help me with this? At this point I'm really frustrated with my decision to upgrade from the perfect '08 530 to this flawed 2012 500. I also noticed that when I rode the new 500 from my home (Utah) at 4700 feet to the top of the mountain I live nearby to 9000 feet the 500 didn't want to idle. My 08 530 never had a problem up there, you would think that this EFI machine would work better than a carburetor, rather than worse.

Thanks guys,

Scott

Last edited by Wizard64; 10-11-2011 at 10:43 AM.
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post #2 of 50 (permalink) Old 10-13-2011, 07:14 PM
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Quote:
Originally Posted by Wizard64 View Post
Hi. I just sold my 2008 530 EXC which was in brand new condition, and purchased a 2012 500 EXC to replace it with and so far I feel I could have made a mistake, and I don't want that to be the case. I feel the EFI isn't properly tuned or something, possibly too lean on idle because it backfires upon deceleration EXTREMELY BAD, and non-stop. I understand that a main cause for backfiring upon deceleration is an exhaust leak but I can't see, hear, or feel any exhaust leak which makes me think that the EFI is just simply tuned too lean on idle or something like that.

Can anyone here please help me with this? At this point I'm really frustrated with my decision to upgrade from the perfect '08 530 to this flawed 2012 500. I also noticed that when I rode the new 500 from my home (Utah) at 4700 feet to the top of the mountain I live nearby to 9000 feet the 500 didn't want to idle. My 08 530 never had a problem up there, you would think that this EFI machine would work better than a carburetor, rather than worse.

Thanks guys,

Scott
sounds like the fuel pressure regulater,but if its new it should be coverd
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post #3 of 50 (permalink) Old 10-16-2011, 11:34 PM
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I am having the same experience - coming off of a very strong running '08 530 and on to a 2012 500 with the same lean issue.

I am, however, that more information will come on this bike on how to tune it to get it running properly. When I first got my 530, it ran like an XR200, then I learned about jetting it properly, a muffler mod and it ran perfect.

I am hoping for the same kind of success on this bike as soon as more information is learned ....
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post #4 of 50 (permalink) Old 10-27-2011, 01:14 AM
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If you remove the cold air pump and filter from the right side of the cylinder head (and plug it with the supplied plug), the lean pop issue disappears.
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post #5 of 50 (permalink) Old 10-29-2011, 11:01 PM
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I am curious to see what fixes KTM has for these bikes, because this seems to be a problem with FI on the thumpers, especially the enduro bikes.

Luke
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post #6 of 50 (permalink) Old 10-30-2011, 08:19 PM
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Same situation

After about 3 hours on my 2012 500 exc the backfire and pop on decel started and has stayed. Dont like it at all. ecavaliere you mention a "supplied" plug. Where would i find that please? I've searched my tool kit and new owners kit etc to no avail.

Thank you all!
Scott
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post #7 of 50 (permalink) Old 10-31-2011, 12:06 AM Thread Starter
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2012 EXC 500 Popping problem solved

Ok, a follow up.... On the 2012 EXC 500 "popping" or backfiring issue that I knew was caused by a lean condition at idle....

I have found by troubleshooting the issue to be 60% caused by the EVAP purge solenoid and EVAP canister system, and the other 40% caused by the SAS valve (secondary air system).
The EVAP purge solenoid system can be disabled by simply unplugging the small two wire connector from the rubber mounted solenoid just under the throttle body (EFI unit) and it will quit allowing outside air into the cylinder. I personally believe that the factory needs to reprogram the ECM/PCM so that the solenoid is NOT energized at idle, but that's my personal opinion, I think they missed the boat in the programming of "when" the EVAP purge solenoid should be open or closed.

HOWEVER, I don't care if they come out with a new program or not because I've learned that it doesn't need to be there anyway, so I've removed the solenoid, the vacuum hoses, the canister (tucked behind the right side of the gas tank) and the little brass fitting that's screwed into the right side of the intake port of the cylinder and replaced the brass fitting with a small metric screw with locktite on the threads. Also to finish up on the removal of the EVAP system you have to re-route the gas tank breather hose to the hole in the frame where it normally goes on the XC-W or other KTM models, or do what I did and purchase the little orange annodized gas cap breather check valve and hose that is way cool looking. (click on the link)
http://www.ktm-parts.com/U6951010.html
This solves 60% of the popping.

Now for the other 40% of the popping... it's caused by the SAS valve, or secondary air system valve and hose. On the right side of the cylinder you'll see an aluminum valve with about a 1/2" or 5/8" diameter black rubber hose attached and the hose runs up and between the right side of the tank and the frame. This system is also for emmissions and not needed in most states (But KTM had to put it there to sell it in the U.S. as a 50-state legal bike). Remove the hose and the valve from the cylinder and then screw in a 12mm x 1.5mm thread x "as short as you can get it" bolt into the threaded hole in the cylinder with the copper washer and locktite on the threads and you're done! I re-used the aluminum locknut that was on the SAS valve to make my bolt essentially shorter than it actually was so I didn't have to cut my bolt shorter... I spun on the aluminum nut onto my bolt then put on the copper washer, then locktite, then threaded it into the cylinder.

One more thing, when you start the bike after the EVAP removal, it won't idle, you'll have to turn the idle up with the idle knob on the left side of the throttle body. THIS IS BECAUSE the idle screw/knob is actually an air screw and since the idle was adjusted stock with all that extra air being allowed into the cylinder, the idle knob was probably like mine, almost all the way screwed in. In fact, you should be able to kill the engine by turning the idle knob all the way in but in STOCK FORM, you cannot turn the idle down far enough to kill the engine because of all the extra air the other two unnecessary systems are allowing into the cylinder at idle.

I now am finally happy with my 2012 EXC 500.
I also rode it yesterday to 9712 feet in elevation and it idled just fine up there now with the modification, where before the mod it wouldn't idle at that altitude.
Very nice bike,

Scott in Utah

Last edited by Wizard64; 10-31-2011 at 12:32 AM.
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post #8 of 50 (permalink) Old 10-31-2011, 01:07 AM
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Quote:
Originally Posted by Wizard64 View Post
Ok, a follow up.... On the 2012 EXC 500 "popping" or backfiring issue that I knew was caused by a lean condition at idle....

I have found by troubleshooting the issue to be 60% caused by the EVAP purge solenoid and EVAP canister system, and the other 40% caused by the SAS valve (secondary air system).
The EVAP purge solenoid system can be disabled by simply unplugging the small two wire connector from the rubber mounted solenoid just under the throttle body (EFI unit) and it will quit allowing outside air into the cylinder. I personally believe that the factory needs to reprogram the ECM/PCM so that the solenoid is NOT energized at idle, but that's my personal opinion, I think they missed the boat in the programming of "when" the EVAP purge solenoid should be open or closed.

HOWEVER, I don't care if they come out with a new program or not because I've learned that it doesn't need to be there anyway, so I've removed the solenoid, the vacuum hoses, the canister (tucked behind the right side of the gas tank) and the little brass fitting that's screwed into the right side of the intake port of the cylinder and replaced the brass fitting with a small metric screw with locktite on the threads. Also to finish up on the removal of the EVAP system you have to re-route the gas tank breather hose to the hole in the frame where it normally goes on the XC-W or other KTM models, or do what I did and purchase the little orange annodized gas cap breather check valve and hose that is way cool looking. (click on the link)
http://www.ktm-parts.com/U6951010.html
This solves 60% of the popping.

Now for the other 40% of the popping... it's caused by the SAS valve, or secondary air system valve and hose. On the right side of the cylinder you'll see an aluminum valve with about a 1/2" or 5/8" diameter black rubber hose attached and the hose runs up and between the right side of the tank and the frame. This system is also for emmissions and not needed in most states (But KTM had to put it there to sell it in the U.S. as a 50-state legal bike). Remove the hose and the valve from the cylinder and then screw in a 12mm x 1.5mm thread x "as short as you can get it" bolt into the threaded hole in the cylinder with the copper washer and locktite on the threads and you're done! I re-used the aluminum locknut that was on the SAS valve to make my bolt essentially shorter than it actually was so I didn't have to cut my bolt shorter... I spun on the aluminum nut onto my bolt then put on the copper washer, then locktite, then threaded it into the cylinder.

One more thing, when you start the bike after the EVAP removal, it won't idle, you'll have to turn the idle up with the idle knob on the left side of the throttle body. THIS IS BECAUSE the idle screw/knob is actually an air screw and since the idle was adjusted stock with all that extra air being allowed into the cylinder, the idle knob was probably like mine, almost all the way screwed in. In fact, you should be able to kill the engine by turning the idle knob all the way in but in STOCK FORM, you cannot turn the idle down far enough to kill the engine because of all the extra air the other two unnecessary systems are allowing into the cylinder at idle.

I now am finally happy with my 2012 EXC 500.
I also rode it yesterday to 9712 feet in elevation and it idled just fine up there now with the modification, where before the mod it wouldn't idle at that altitude.
Very nice bike,

Scott in Utah
Thanks Scott!

Great info there - I have experimented a bit my 500exc with similar results. Removing the SAS system was a huge improvement, and when I removed the EVAP system my bike would not idle (as you described). I pretty much chickened out from there and re-installed the EVAP system. It sounds like I just need to turn up the idle and I'll be good to go - great news. How much time and how many miles have you put on your bike since removing all of this equipment? It sounds like you have been "trouble free" since removing all the extra equipment, and that is what I am hoping to hear.

Thanks again!
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post #9 of 50 (permalink) Old 10-31-2011, 01:10 AM
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Quote:
Originally Posted by Scottkearns View Post
After about 3 hours on my 2012 500 exc the backfire and pop on decel started and has stayed. Dont like it at all. ecavaliere you mention a "supplied" plug. Where would i find that please? I've searched my tool kit and new owners kit etc to no avail.

Thank you all!
Scott
Scott,

The plug I am describing was supplied in the PDI bag along with the mirrors, tool kit, etc. If you did not get one, you can order the plug off of the '12 500xc-w.

Good Luck!
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post #10 of 50 (permalink) Old 10-31-2011, 10:27 AM
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Incredible info Gents! I plan to get started right away on this one!

Again, MUCH APPRECIATED!

Scott
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